Isolation of the algal symbiont and the role of vitamins in growth, heterocyst development and nitrogen-fixing activity

Nitrate-free medium supplemented with growth regulators such as 2,4-D, NAA and IBA was used to isolate. Two isolates grew adequately in the N-free Allen and Arnons medium. Incorporation of biotin and pantothenic acid stimulated the growth and heterocyst frequency of one of the isolates. This isolate also exhibited higher nitrogenase activity and excreted a higher amount of ammonia.